Elongated, flexible guidewires have been used in the prior art to position both diagnostic and therapeutic catheters within a patient. Catheters used in diagnostic angiography allow a contrast liquid to be injected through a catheter center passageway into a patient blood vessel to study blood flow patterns within the blood vessel. Coronary studies, for example, are typically conducted utilizing catheters which are positioned within the coronary artery with the aid of a flexible guidewire.
Within the last decade, specialized balloon catheters have been used to expand occluded blood vessels to increase blood flow through those vessels. The balloon catheter is inserted into the patient over the guidewire and properly positioned prior to its inflation.
The step of inserting a catheter, whether it is for diagnostic or therapeutic purposes, is often accomplished using a guidewire to steer the catheter into a proper position in the patient's cardiovascular system. The catheter's distal end can be more easily positioned if it follows the guidewire and is pushed over the guidewire to an appropriate position.
One prior art guidewire includes a distally located flexible tip portion that can be routed into the patient and maneuvered by monitoring progress of the guidewire on an x-ray imaging system. The distal tip can be constructed from a highly opaque material to facilitate this monitoring of the guidewire as it is inserted. Issued U.S. Pat. Nos. 4,545,390 to Leary and 4,538,622 to Samson et al. disclose representative prior art guidewire constructions.
Problems are often encountered as the physician attempts to route a guidewire through an obstructed region of a blood vessel while inserting a catheter. Prior art techniques for inserting the guidewire typically comprise the steps of jabbing the flexible distal tip portion of the guidewire against the obstructed region in hopes of finding a passageway through the obstruction. If the blood vessel is totally blocked by plaque or the like, these efforts fail and it becomes impossible to route the catheter to a proper position.